A ground fault circuit breaker wherein ground fault interrupting capability is combined with the overload and short circuit interrupting capability of conventional automatic electric circuit breakers is described within U.S. Pat. No. 4,037,185 in the name of Keith W. Klein. Both the ground fault circuit interruption circuit and overcurrent interruption circuit are electrically interconnected and arranged within a partitioned molded case. The electrical interconnection between the ground fault and overcurrent circuits is difficult to achieve on automated assembly equipment for this ground fault circuit breaker design.
Ground fault circuit interrupters (GFCI) having a magnetic sensor module plug-in subassembly which is capable of being assembled in a completely automated process is described in U.S. patent application Ser. No. 579,336 filed Feb. 14, 1984 in the names of R. A. Morris et al. entitled "Electrical Interconnect Arrangement For GFCI Magnetic Sensor Module Plug-In Subassembly" and should be referred to for a detailed description of the electrical and mechanical interconnection of the components making up the signal processor circuit board for the GFCI device. The circuits for such devices are described in U.S. Pat. Nos. 4,345,289 and 4,348,708, both of which are in the name of Edward K. Howell. The circuits described therein basically include a current sensor, a signal processor and an electronic switch. An imbalance is determined in the line and neutral conductors of the distribution circuit by means of a differential current transformer and is amplified by the signal processor pursuant to triggering the electronic switch and completing the energization circuit for a trip solenoid. The current sensor also includes a neutral excitation transformer for responding to a ground fault on the neutral conductor. Both of these patents are incorporated herein for purposes of reference.
It has since been determined that an automated ground fault circuit breaker can be provided by the modular combination of the signal processor printed circuit board with the ground fault module, which includes ground fault interruption facility, and the circuit breaker module, which includes short circuit protection as well as short time and long time overcurrent protection. The signal processor module, the ground fault module and the circuit breaker module are first individually assembled by means of independent automated assembly processes, before being automatically assembled together to form the ground fault circuit breaker unit. This automated modular concept results in a substantial savings of assembly time while synergistically improving the overall response and reliability of the assembled product.